1. Field of the Invention
The present invention generally relates to culvert thawing devices and more specifically to a guide pipe for passing a culvert thawing tube with a power head into a culvert.
2. Description of Related Art
During periods of cold weather, water draining through underground culverts tends to freeze, choking the culvert with ice. This phenomenon is especially prevalent in northern localities. Before warmer weather thaws the ice within the culverts, and reestablishes communication therethrough, the water from the melting snow floods the roadbed and greatly impairs the same by washing gullies therein.
Various methods have been set forth to prevent these and similar disastrous results caused by freezing culverts. Examples of methods and devices generally related to this art include U.S. Pat. No. 77,857 issued May 1868 to Young (Clearing Pipes); U.S. Pat. No. 678,118 issued July 1901 to Kruschke (Heating Attachment for Culverts); U.S. Pat. No. 827,025 issued July 1906 to Liddle (Device for Thawing Frosted Hydrants, Water Mains, and Service Pipes from Mains to House Hydrants); U.S. Pat. No. 980,314 issued January 1911 to McGill (Snow Melter for Manholes or Sewer Pipes); U.S. Pat. No. 1,253,692 issued January 1918 to Kampff (Thawing Device for Hydrants); U.S. Pat. No. 1,292,941 issued January 1919 to Winters (Means for Thawing out Sewers); U.S. Pat. No. 1,294,888 issued February 1919 to Farrell & Maier (Means for Thawing Frosted Fire Hydrants, Water Mains, and the Like); U.S. Pat. No. 4,770,211 issued September 1988 to Ollson (Method for Thawing Out Road Culverts Choked with Ice). These inventions disclose methods which generally fall within two categories.
One method includes pre-placing thawing pipes within the culvert. Upon freezing of the culvert, high-pressure steam is passed through the thawing pipes. The heat produced by the steam is thermally conducted through the wall of thawing pipe to melt the surrounding ice. Use of these thawing pipes presents various problems. While heating pipes are effective in melting ice directly surrounding the heating pipe, they are ineffective in heating remote portions of the culvert. This is because the temperature profile of the water/ice slurry surrounding the pipe rapidly decreases at a rate roughly proportional to the square of the distance from the pipe. Thus, heating pipes only reestablish small, annular passages therearound. Also, heating pipes must therefore run along the entire length of the culvert to be effective. But providing long culverts with thawing pipes is expensive, and providing multiple culverts under long stretches of highway with more than a small number of culvert thawing pipes quickly becomes cost-prohibitive. Finally, the severe temperature gradients and cyclic temperature changes experienced by the thawing pipe walls encourage crack propagation and lead to breaches therethrough. Once the integrity of the thawing pipe is breached, the steam intended to be passed therethrough, instead escapes into the culvert. When this happens the thawing pipe becomes ineffective in thawing the culvert downstream of the breach.
A second method for re-establishing communication through a culvert entails running a flexible steam tube with a power head into and through the frozen culvert. A power head, or a rat, is a specially-formed nozzle which is attached to the discharge end of a flexible steam tube. The rat has a forward discharge orifice which discharges steam in a forward direction to melt the ice. The rat also has a plurality of rearward discharge orifices which discharge steam at a greater force than the steam exiting forward discharge orifice, thereby propelling the rat forward through the culvert. As the steam leaving a rat is not constrained by a heating pipe, the steam more effectively thaws culvert ice. Because rats are more effective than heating pipes, the rats are more commonly used.
However, rats also have a drawback. Culverts are generally located deep below the ground surface. Culvert openings are commonly accessible by manholes and ladders. Other manholes open into ditches or creeks, at the bottom of embankments. Thus, on those occasions in which the culvert opening needs to be accessed in order to insert the rat, the culvert opening is often covered by numerous feet of ice, snow or ice-water slurry. Under these circumstances, insertion of the rat into the culvert opening is difficult at best, and further, can even be dangerous. First, merely locating the snow-covered culvert opening or manhole can prove difficult and time-consuming. Once the location is determined, accessing the culvert opening is a second, not inconsiderable task. The maintenance personnel must first dig through the snow and then chisel through the ice which is covering the culvert opening. This is strenuous, time-consuming work which must be carried out in sub-freezing temperatures, and often, undertaken in dangerous locations such as at the bottom of steep inclines and near chilling, snow-obscured creeks. Preferably, the rat should not be used for this task because the rat must be operated within a sleeve or pipe to guide the movement of the rat's flexible hose. Otherwise, the hose can whip in an uncontrolled manner and the rat can easily change direction, discharging high-pressure steam at the maintenance workers. Even if the rat is used, significant excess energy must be expended unnecessarily to generate the steam for melting the large body of ice situated above the culvert opening.
Therefore a need still exists for a device which enables easy introduction of a rat into a culvert for thawing ice therein. None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.